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Multi-sclae Modeling for Determination of Thermal Properties of Silicon Nanostructures Via Molecular Dynamics (MD) and Finite Element Method (FEM)

DorMohammadi, Hossein | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 44664 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khoei, Amir Reza
  7. Abstract:
  8. The band gap offset is an effect of coordination numbers (CNs) of atoms reduction at the edge of transversal cross-section Si nanowires (SiNWs) which would be of increasingly important for greater shell-core ratio sections. In this paper, a hierarchical multi-scale modeling has been developed to simulate edge effect on the band gap shift of SiNWs due to geometry effect induced strain in the self-equilibrium state. Classical Molecular Dynamics (MD) approach and Finite Element Method (FEM) are used in the micro (atomic) and macro scale levels, respectively. Using the Cauchy-Born (CB) hypothesis as a correlator of continuum and atomic properties, the atomic positions are related to the continuum field through the deformation gradient. To capture the surface, edge and corner effects, the radial quadrature is used in the surface elements which is conceptually an indicator of material behavior. The information for each quadrature point is gathered by data interpolating from atoms laid in a circular support around the quadrature, in a least square scene. Finally, the applicability of proposed model is illustrated in numerical simulation of four cross-section SiNWs (circle, hexagon, rectangle and triangle) and comprising their results with fully atomistic model (MD), and the analytical results.

  9. Keywords:
  10. Multiscale Modeling ; Edge Effect ; Band Gap Shift ; Silicon Nanowire ; Cauchy-Born Rule ; Molecular Dynamics ; Finite Element Method ; Surface Effect

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